s390/virtio_ccw: Fix config change notifications

Commit e3e9bda3 ("s390/virtio_ccw: use DMA handle from DMA API")
broke configuration change notifications for virtio-ccw by putting the
DMA address of *indicatorp directly into ccw->cda disregarding the fact
that if !!(vcdev->is_thinint) then the function
virtio_ccw_register_adapter_ind() will overwrite that ccw->cda value
with the address of the virtio_thinint_area so it can actually set up
the adapter interrupts via CCW_CMD_SET_IND_ADAPTER.  Thus we end up
pointing to the wrong object for both CCW_CMD_SET_IND if setting up the
adapter interrupts fails, and for CCW_CMD_SET_CONF_IND regardless
whether it succeeds or fails.

To fix this, let us save away the dma address of *indicatorp in a local
variable, and copy it to ccw->cda after the "vcdev->is_thinint" branch.

Fixes: e3e9bda3

 ("s390/virtio_ccw: use DMA handle from DMA API")
Reported-by: Boqiao Fu <bfu@redhat.com>
Reported-by: Sebastian Mitterle <smitterl@redhat.com>
Closes: https://issues.redhat.com/browse/RHEL-39983
Tested-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Eric Farman <farman@linux.ibm.com>
Signed-off-by: Halil Pasic <pasic@linux.ibm.com>
Link: https://lore.kernel.org/r/20240611214716.1002781-1-pasic@linux.ibm.com
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>